Sun Microsystems contends that by failing to implement the Java Native Interface (JNI) in its virtual machine, Microsoft prevents valid Java programs from operating correctly. In addition, Sun claims that Microsoft's inclusion of three additional compiler directives (@DLL, @COM and @SECURITY) and two additional keywords (DELEGATE and MULTICAST) produces an incompatible variant of the language. (For details on these issues, see Bill Day's accompanying article, .) In response to Sun's claims, Microsoft argues that the contract between the two parties gives it the right to make such extensions.